1. Field
The following description relates to a wireless communication apparatus, and more particularly, to a maritime wireless communication apparatus.
2. Description of the Related Art
As maritime communication is a very old form of communication, it has evolved slowly compared to other communication technologies since it is difficult to build the wired/wireless communication infrastructure at sea. With the recent rapid advance of communication technology, however, maritime communication is also in the process of being modernized. Under the leadership of International Maritime Organization (IMO), e-Navigation policy has been internationally pursued in an effort to provide safety and security at sea and also protect marine environment by electronically collecting, integrating, exchanging, representing, and analyzing maritime information on ships and shores, and the importance of Ship to Ship, Ship to Shore (4S) communication has been underscored.
Although being equipped with a VHF communication device, most maritime ships generally depend on an analog voice-based communication, except when transmitting a text message, and ocean-going sailing ships have to rely on low-speed, yet costly satellite communications. Most small fishing vessels, which account for the majority of vessels, have operated without any communication devices to ensure minimum safety at the risk of human lives. Many ships operate offshore, but it is difficult for them to be provided with various services from land since there is no maritime wideband digital communication network. Also, although the existing land communication networks, such as the cellular phone networks, are used for maritime communication, they have, however, limited communication range, and it would be problematic for the ships sailing to various areas to use such networks, so that it is not easy to actively utilize the land communication networks.
Research on the modernization of maritime communications has been recently conducted, including development of ITU-R M. 1842-1-based maritime digital VHF wireless communication system and the application of WiMAX Mobile Multi-hop Relay (MMR) technology or wireless local access network (LAN) technology to the maritime communication. The modernization of the maritime communication that relies on an analog voice-based communication to a digital data communication is in progress.
Technologies for new maritime broadband wireless communication infrastructures may relate to a satellite communication, the existing maritime communication, and a terrestrial communication. It is fundamentally hard to lower the price of the satellite communication, or to increase the speed of the existing maritime communication. In addition, the terrestrial communication technology that uses ultra-high frequency (UHF)/SHF bands may have problems regarding distance range, whereas such problems may be overcome by expanding the distance range through multi-hop relay technology, the high-performance amplifier development and use of directional antennas.
In the application of the terrestrial broadband wireless communication technology to the maritime communication, there is a problem in that a frequency band greater than UHF band used for terrestrial communications has a distance range shorter than MF, HF, and VHF frequency bands used for maritime communications. To alleviate the problems, a directional antenna may be used, rather than an omni-directional antenna, so as to extend the transmission range and simultaneously improve space reuse gain. However, since the directional antenna emits strong radio waves only in a certain direction and has characteristic sensitivity that is increased with respect to radio waves from a certain direction, the directional antenna has been used for Point-to-Point (P2P) communication between fixed stations in terrestrial long distance communication, but it is not suitable for Point-to-Multipoint (P2M) communication between ships sailing at sea.